1. Field of the Invention
The present invention relates to a drive circuit and a drive method for a panel display device, and particularly to a drive circuit and a drive method for a panel display device which are capable of charging light-emitting devices at high speed.
2. Description of the Related Art
FIG. 9 illustrates an organic EL panel display device which has organic EL devices PEP,Q (P is an integer ranging from 1 to m; Q is an integer ranging from 1 to n) arranged at respective intersections between a plurality of data lines (anode lines) SEG1 to SEGm (m is an integer no smaller than 2) and a plurality of scan lines (cathode lines) COM1 to COMn (n is an integer no smaller than 2). A drive device of this organic EL panel display device has switch circuits SWs1 to SWsm for connecting the data lines SEGP to respective constant current sources 11, and switch circuits SWc1 to SWcn for connecting the respective scan lines COMQ to a power supply potential (Vcc) 20. A drive control circuit 10, or output control means, controls these switch circuits SWsP and SWcQ to select/deselect the organic EL devices PEP,Q.
Now, typical operation for causing the organic EL panel display device to emit light for display will be described with reference to operating waveforms shown in FIG. 10. When the switch circuits SWcQ connecting to the scan lines COMQ are turned ON and OFF at a certain period of interval (which defines one frame), the scan lines COMQ on which the organic EL devices PEP,Q to be lit are arranged are sequentially selected. Here, the turned ON state is selected by connecting the scan lines COMQ to a ground potential Vss. The turned OFF state is selected by connecting the scan lines COMQ to the power supply potential Vcc. A single frame period P0 is typically composed of a discharge period P1 for discharging electric charges stored in the organic EL devices PEP,Q, and a charge period P2 for turning ON a single scan line COMQ to cause the selected organic EL device PEP,Q to emit light.
In the charge period, the switch circuit SWsP on the data line SEGP that is connected with the selected organic EL device PEP,Q is turned ON to connect the data line SEGP to the constant current source 11. As a result, the current from the constant current source 11 is supplied to cause the organic EL device PEP,Q to emit light. Here, the rows of the unselected scan lines COMQ and the unselected organic EL devices PEP,Q might undergo crosstalk and cause emission defects due to half-excited states of the organic EL devices PEP,Q. To avoid this, control is usually performed to supply the potential of a power supply voltage level to the scan lines COMQ and to supply a potential of the GND level to the data lines SEGP, thereby applying reverse biases to the organic EL devices PEP,Q.
In the discharge period, for the sake of preventing residual charges in the previous frame from causing emission defects in the next frame, the ground potential Vss is applied to all the data lines SEGP and the scan lines COMQ, thereby resetting charges stored in the organic EL devices PEP,Q to zero (the organic EL devices PEP,Q are zero-biased).
A related art of a drive circuit for an organic EL panel display device is disclosed, for example, in Japanese Patent No. 3507239.
In the related art of the drive circuit and the drive method for a panel display device, however, constant current sources are used for charging. The rise time required for charging up to a voltage necessary for light emission is long, thus causing such problems as deteriorated emission intensities of the organic EL devices PEP,Q and uneven display (variations in brightness).